In a known thermal overcurrent relay, a thermal bimetal is provided for each phase, the free bent-out ends of which act on a slider by means of which a double-arm lever is actuated, which acts via a further slider on a leaf spring, which is clamped at one end, to the free end of which an arm of a U-shaped snap-action spring is linked, the other arm of which acts on a contact leaf spring. At its free end, the contact leaf spring has a moving contact piece, which, together with a fixed contact piece, forms a contact point. In a first position, the contact point is closed and when the second slider is moved, the leaf spring is bent until the linking point of the snap-action spring reaches its dead point position; when the second slider is moved further, the snap-action spring snaps over and opens the contact point.
Similar arrangements can be found in a large number of variants in other snap-action switch elements.
In these known arrangements, a reduction in the contact force and/or a relative movement in the contact point usually occurs before the contact actually opens. Furthermore, it is usually possible and also necessary to adjust the snap-action device.